1. Field
Example embodiments relate to liquid crystal display devices, for example, cholesteric liquid crystal display devices, and methods of manufacturing the same.
2. Description of the Related Art
As flexible displays such as electronic paper (e-paper) are actively developed, display devices using cholesteric liquid crystals are receiving more attention.
A cholesteric liquid crystal is a liquid crystal composition formed by twisting liquid crystal molecules of a nematic liquid crystal into a helix structure. A cholesteric liquid crystal has light reflection and transmission properties which vary according to a helix pitch. For example, light having a given, desired or predetermined wavelength range is selectively reflected according to a helix pitch of twisted liquid crystal molecules. Cholesteric liquid crystals can produce a full-color image by controlling a wavelength reflection band by using pixels having different helix pitches. A cholesteric liquid crystal display device having these display characteristics has relatively clear color display characteristics, relatively high contrast characteristics, and relatively high resolution characteristics. Moreover, a display device using cholesteric liquid crystals shows relatively high performance.
Conventionally, full-color images are produced using single layer or multilayer cholesteric liquid crystal displays. In a single layer cholesteric liquid crystal display device, the red (R), the green (G), and the blue (B) pixels are arranged in the same plane. By contrast, in a multilayer cholesteric liquid crystal display, a red (R) pixel, a blue (B) pixel and a green (G) pixel are stacked on each other.
In both single layer and multilayer cholesteric liquid crystal displays, the red (R) pixel has a helix pitch that is controlled such that light having a red wavelength range is selectively reflected, the green (G) pixel has a helix pitch that is controlled such that light having a green wavelength range is selectively reflected, and the blue (B) pixel has a helix pitch that is controlled such that light having a blue wavelength range is selectively reflected.
In a multilayer cholesteric liquid crystal display, respective pixels are controlled to be in a selective reflection mode or transmission mode according to the application of a voltage, and a color corresponding to a pixel in the wavelength selection reflection mode is displayed. However, multilayer cholesteric liquid crystal displays are relatively complicated and relatively expensive to manufacture because a multilayer substrate is used. In addition, the multilayer cholesteric liquid crystal displays also provide relatively low color purity due to a scattering phenomenon, which may occur in a pixel that is in the transmission mode.